Dogs Can Feel Envy, Study Suggests

The first scientific study to find envy in non-primates affirms what many already know: dogs can get jealous.

"Everybody who has a dog at home probably [suspects] that dogs can be very jealous of other dogs and also of people," said lead author Friederike Range of the University of Vienna, Austria.

In experiments with 43 dogs, Range's team showed that the canines reacted to inequity.

The team had one dog watch another dog receive a reward for doing a trick. When the watching dog performed the same trick and was not rewarded, that dog refused to do the trick again, Range said.

The experiments were modeled after recent studies that observed resentment in capuchin monkeys and chimpanzees when the animals weren't compensated equally after performing the same tasks as a partner.

Dogs are not as sensitive to inequality as the primates, Range and her team found. The canines participating in the study didn't seem to mind if a nearby dog got a better reward or didn't work as hard for the reward—but the primates did.

The study was published online today in the journal Proceedings of the National Academy of Sciences.

Range and her team tested the dogs in the presence of partner dogs they were already acquainted with—a playmate, or a pet from the same household.

The dogs were asked to place their paws in the experimenter's hand. The animals were rewarded—or not—with dark bread and sausage.

"If both of them didn't get a reward, they continued working more or less," Range said. "But if one of them didn't get food, the one that didn't get food just said, No."

The indignant dogs' refusal to participate further was accompanied by scratching, yawning, mouth licking, and avoiding the gaze of the partner dog as well as the experimenter.

The dogs didn't seem to worry if their partner got sausage—a premium treat—and they only got bread, or if the other dog didn't perform the trick but was rewarded anyway.

"It gets more complicated if it's about both effort and the reward, and maybe dogs can't do that yet," Range suggested.

Dogs' more basic form of envy—and the insistence on some degree of equality—is probably critical to survival in cooperative activities. Wolves and wild dogs are known to hunt and raise their pups in groups, where individuals who don't insist on compensation would likely be taken advantage of.

Primatologist Frans de Waal at Emory University in Atlanta, Georgia, said he would expect this kind of envy—really an aversion to unequal reward—in all animals that regularly cooperate.

"The dogs showed a stronger reaction when they received nothing for the task in the presence of a rewarded companion than with no companion at all," he noted.

"They were OK with no reward if no one else got one, which shows that it is a social reaction."

Scott Creel, a behavior ecologist at Montana State University, said the research suggests many social species may have mental processes scientists once believed were unique to humans, or at least primates.

"It seems logical that many of the same selection pressures that have shaped our cognition and emotions also operate in other social species," said Creel, who has studied the behavior of African wild dogs but was not involved in this study.